The present invention relates to a new tire rasp blade for use in tire buffing machines.
The disclosures of U.S. Pat. Nos. 5,033,175, 4,019,234 and 2,703,446 are incorporated herein by reference into this application.
Tire buffing machines are well known in the tire retreading industry. Conventionally, a tire buffing machine includes both a structure for mounting a used tire and a rasp hub which removes the worn tread from the used tire prior to the retreading process. The used tire is rotated while it is held against the rapidly rotating rasp hub whose outside perimeter is provided with a multitude of tire rasp blades. When so engaged against the used tire, the blades cut or shear small segments of rubber from the worn tread surface area of the tire. In this way, the tire is "buffed" to remove the unwanted used tread and to achieve an evenly textured surface suitable for retreading.
Tire rasp blades, together with intervening spacers, are assembled on the periphery of the rasp hub between the hub front and back plates. U.S. Pat. Nos. 2,703,446 and 4,019,234 disclose such conventional prior art rasp hub assemblies wherein the back plate of the hub has axially directed support pins on which are mounted the rasp blades and spacers. The front plate is then assembled onto the support pins against the assembled blades and spacers and locked into place.
Use of bent blades with flat spacers is described in U.S. Pat. No. 5,033,175. This arrangement creates a circumferentially interlocked hub with less potential for mechanical failure at high rotational speeds.
It has been conventional practice to form the outer-most portion or "working edge" of the tire rasp blade as a segment of a circle. That is, the working edge is in the form of an arc defined by a common radius. However, when such tire rasp blades are assembled into a hub, they are inclined relative to the direction of rotation of the hub. As a result, the actual geometry of the working edge of each blade--as it is rotated on the hub--is no longer circular relative to the surface of the tire being buffed. In effect, as the buffing hub rotates, the working edge of the inclined tire rasp blades cyclically move toward and away from the surface of the tire. This, in turn, causes inefficient operation and uneven buffing of the tire.